Dual spark ignition system

ABSTRACT

An engine ignition system connectible to a source of electrical energy and comprising a timing device for providing first and second timing signals and a triggering device for providing first and second electrical triggering signals of opposite polarity in response to the first and second timing signals, respectively. An electronic switch is closed in response to each of the triggering signals and each closing of the switch causes a capacitor to discharge. The energy discharged from the capacitor is used to provide a spark for ignition of fuel in the engine.

11 States Patent 1191 Howard Feb. 18, 1975 15 1 DUAL SPARK IGNITION SYSTEM 3118125 2/1973 Posey 123/148 DC [76] Inventor: Homer E. Howard 2024 Paloma Dr Costa Mesa, (Balm 92627 Przr nary Eramzrzer-Charles J. Myhre Assistant I;.tam1nerRona1d B. Cox [22] Filed: Feb. 12, 1973 Attorney, Agent, or Firm-Gordon L. Peterson '21] Appl. No.: 331,685

[57] ABSTRACT 52 1.1.5. (31.. 123/148 BC, 123/148 E, 315/209 co t 9 ignmo sgstem 1 a soLfmefof [51 1111.01. F02p 1/00 6 1". i P or [58] Field 01 Search 123/148 E, 148 DC, 148 D; P f first and f mg device for providing first and second e1ectncal trig- 315/209 CD germg signals of opposite po1ar1t3/ in response to the [56] References Cited first and second timing signa1s, respectively. An elec:

tronic switch is closed in response to each of the trig UNITED STATES PATENTS gering signals and each closing of the switch causes a 3180.809 10/1966 ls sler 123/148 DC a a itor to discharge. The energy discharged from 3500308 3/1970 mskl 123/148 DC the capacitor is used to provide a spark for ignition of 3520288 7/1970 Dusenberry.... 1. 123/148 E fuel in the engine 3.554178 1/1971 Boyer 1 123/148 E 3636936 1/1972 Schuette 123/148 DC 14 Claims, 9 Drawing Figures CHA/PG/A/G CIRCUIT DUAL SPARK IGNITION SYSTEM BACKGROUND OF THE INVENTION Internal combustion engines are inefficient devices. This is due in part to incomplete combustion of the fuel-air mixture in the combustion chamber. Incomplete combustion not only contributes to poor engine efficiency, but more importantly, to atmospheric pollution in that unburned hydrocarbons are injected in large quantities into the atmosphere.

The ideal time for the spark plug to provide the ignition spark is at or near top dead center of the compression stroke. Unfortunately, the energy content of the spark is too low at top dead center to properly ignite the fuel-air mixture. Accordingly, it is common practice to advance the spark and thereby reduce the re quired energy content of the spark for ignition. However, advancing the spark in the typical four-stroke cycle engine results in considerable combustible fuel passing out of the exhaust in an unburned condition.

In an effort to overcome this problem, it has been proposed to provide multiple sparks per cylinder per power stroke. While this is a sound concept, prior art implementations have serious drawbacks. For example, one prior art device employs two complete ignition systems including two coils, two distributors, and two spark plugs per cylinder to supply two sparks per cylinder per power stroke. The duplication of components in this system is expensive. In addition, significant mechanical changes are necessary to provide the drive for the two distributors and special cylinder heads are needed to accommodate two spark plugs per cylinder.

In a second prior art system, oscillating or alternating voltage is applied to the spark plugs for the entire pe riod of time that the points are open. The spark voltage in this system is too low in energy content to provide proper ignition.

SUMMARY OF THE INVENTION The present invention increases engine efficiency and performance and reduces exhaust emissions by utilizing multiple sparks per cylinder per power stroke. This sytem provides the normal or advanced spark for smooth running and a second spark for the same combustible charge. The second spark can occur, for example, at or near top dead center. With the present invention, only one ignition system is required and no mechanical modification of the engine or the distributor drive are necessary.

The results of using the dual spark ignition system of this invention are quite dramatic. Specifically, it produces easier starts, faster warmups, better acceleration, and substantially improves combustion efficiency. This latter advantage in turn reduces exhaust pollutant emissions.

One feature of the invention is to adapt a capacitor discharge ignition system so that it supplies multiple sparks per cylinder per combustible charge. An advantage of using a capacitor discharge system is that at least some of these systems can generate energy for two sparks in a short time period. For example, the capacitor discharge ignition system disclosed in applicants U.S. Pat. No. 3,704,699 is capable of providing two sparks in the requisite time period.

In a capacitor discharge ignition system of this type, an ignition capacitor is charged and then discharged when an electronic switch such as a silicon controlled rectifier (SCR) is rendered conductive. Discharging of the ignition capacitor provides the requisite energy for the spark. In the system disclosed in U.S. Pat. No. 3,704,699, the SCR is rendered conductive by a positive triggering signal which is applied to its gate so that the gate potential becomes positive with respect to the cathode potential. This triggering signal is in turn pro vided by a triggering capacitor which is coupled to a source of electrical energy and to the ignition system timing device such as the points. Each time the points open, a positive triggering signal in the form of a voltage spike appears at the gate of the SCR to render the latter conductive. When the points close, the triggering capacitor discharges with the result that a negative voltage spike appears, but this does not trigger the SCR. Thus, the SCR is triggered with each of the positive signals or once for each combustible charge.

One feature of the present invention is that it employs the negative voltage spike as a triggering signal for the SCR to provide a second spark for the same combustible charge. This can be advantageously ac complished by applying the negative voltage spike to the cathode of the SCR while maintaining the gate at a reference potential. This causes the gate potential to be positive with respect to the cathode, and the SCR is triggered a second time to discharge the ignition capac itor to provide the second spark.

The present invention also provides for timing of the triggering signals so that the two sparks occur at the desired times. This can be accomplished by providing timing signals to the triggering capacitor. For example, the timing signals may be provided by a square wave voltage signal with each sharp change in the voltage level constituting a timing signal.

The timing signals are provided by timing devices. All engines have timing devices such as the conventional points, and the present invention uses the normal engine timing device and provides an auxiliary timing device which is operative to simulate closure of the points.

In a preferred embodiment, a conductive path is provided which is coupled to the source of electrical energy and to a reference potential. This conductive path is coupled to the usual timing device such as the points at a junction and to the auxiliary timing device which may include an electronic switch in the conductive path for opening and closing the second conductive path. The junction is, therefore, at a first potential when the points are open and the electronic switch is nonconductive. The junction is at a second potential when either the points are closed or the electronic switch means is conductive. It is this change of potential at the junction which constitutes the timing signals and which causes the triggering capacitor to provide triggering signals.

With this arrangement the first spark is provided in response to opening of the points. The second spark is provided in response to point closure or closing of the electronic switch, whichever occurs first.

The electronic switch is responsive to the first timing signal for closing a predetermined interval thereafter. For example, a resistance-capacitance circuit can be advantageously coupled to the conductive path to thereby render the electronic switch conductive a predetermined time following the first timing signal. The time constant of the RC circuit can be adjusted to pro vide the desired time interval between sparks.

The invention can best be understood by reference to the following description taken in connection with the accompanying illustrative drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view of an engine ignition system constructed in accordance with the teachings of this invention.

FIG. 2 is a plot of voltage at a junction Jl vs. time with each change of potential constituting a timing signal. The effect of the auxiliary timing device is not shown in FIG. 2, and accordingly the variation in voltage is brought about by opening and closing of the points.

FIG. 3 is a plot of voltage vs. time at a junction J2 with each voltage spike constituting a triggering signal.

FIG. 4 is a plot of voltage at the gate of the SCR with respect to voltage at the cathode of the SCR vs. time.

FIG. 5 is a plot similar to FIG. 4 showing the effect of the auxiliary timing device on the gate voltage.

FIG. 6 is a plot similar to FIG. 2 showing the effect of the auxiliary timing device on the timing signals.

FIG. 7 is a plot of voltage at the gate of the SCR of the auxiliary timing device vs. time.

FIG. 8 is a plot similar to FIG. 3 showing the effect of the auxiliary timing device on the triggering signals.

FIG. 9 is a plot of voltage at the junction J1 vs. crank angle showing how point opening and closing varies with engine speed.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows an engine ignition system 11 coupled to a source of electrical energy in a form of a battery 13 which may be the usual automobile battery. The battery 13 supplies direct current to a charging circuit 15 which in turn supplies power to an ignition capacitor 17. The charging circuit 15 may be of any type suitable to rapidly and repeatedly charge the ignition capacitor 17. For example, the charging circuit 15 may include an oscillator, a transformer, and a rectifier substantially as shown in applicants U.S. Pat. No. 3,704,699.

The battery 13 also supplies electrical energy to a junction J1 through a resistor 19 which may be of the order of 30 ohms and provides a current limiting function. A first ignition timing device which, in the embodiment illustrated is in the form of a conventional breaker points 21, is coupled to the junction J1. It

should be understood, however, that breaker points 21 are shown merely by way of example and that any device which provides engine timing signals can be utilized. As is well known, the points 21 have two states, i.e., open and closed. The breaker points 21 are driven by the engine (not shown) with which the ignition system 11 is being used, and thus the points 21 open and close at a rate controlled by the engine rpm. When the points 21 are closed, the junction J 1 is placed at a reference potential indicated as ground in FIG. 1, and when the points 21 are open the junction J1 is at a positive potential above ground. A capacitor 23, which is the conventional automotive system condenser, is coupled across the points 21 in a conventional manner.

A second or auxiliary timing device 25 is also cou pled to the junction J1. The timing device is a preferr d but optional feature of the present invention, and accordingly the construction and operation of the ignition system 11 is considered in FIGS. 2-4 without reference to the timing device 25. Without regard to the timing device 25, the voltage at the junction J1 varies with the opening and closing of the points as shown in FIG. 2 and forms a square wave as shown in FIG. 2. Specifically, the voltage at the junction J1 varies from a reference voltage such as O when the points are closed to a positive voltage V when the points are open. Each change of potential from O to V or from V to 0 constitutes a timing signal. Thus, each change of state of the points 21 provides a timing signal. In FIG. 2, it is assumed that the engine is running at a constant speed.

A triggering capacitor 27 is coupled to the junction J1 and to a junction J2. When the system 11 is first energized and the potential at the junction J1 first rises to V,, the triggering capacitor 27 conducts momentarily so that the voltage at a junction J2 rises sharply to a value V (FIG. 3). This provides a positive voltage spike 29 or a first triggering signal. However, this voltage rapidly decays at the junction J2to a reference value which is shown by way of example in FIG. 3 as 0. During the time that the voltage at J1 remains at V the capacitor 27 is being charged to a voltage of V When the points 21 close, the potential of the junction J1 returns to the reference value of O, and the capacitor 27 discharges. This causes the voltage at the junction J2 to swing sharply to a negative value V or a value below the reference voltage. This provides a negative voltage spike or triggering signal 31 which gradually returns to 0 potential.

Thus, the voltage spikes 29 and 31 constitute triggering signals of opposite polarity. The triggering signal 29 occurs each time the potential at the junction J 1 increases from O to V, such as when the points open. The timing signal 31 occurs each time that the voltage at the junction J1 drops from V, to 0 such as when the points close. The triggering signals 29 and 31 are produced repetitively as shown in FIG. 3.

The discharging of the ignition capacitor 17 is con trolled by an SCR 33 and the SCR is in turn controlled by the triggering signals 29 and 31. Specifically, the triggering signal 29 forward biases a diode 35 which is coupled to the junction J2 and to the gate of the SCR 33. Consequently, a gate signal 36 (FIG. 4) in the form of positive voltage pulse having a magnitude V appears at the gate of the SCR 33. This causes the SCR to be rendered conductive inasmuch as the voltage at the gate is made positive by a predetermined magnitude with respect to the potential at the cathode. When the SCR 33 is conductive the ignition capacitor 17 discharges through the SCR 33 and a diode 37 to ground. When the ignition capacitor 17 discharges, an electrical current is developed in the primary of a transformer 39 which produces a corresponding current in the secondary transformer. The transformer 39 steps up the voltage and applies it to a distributor 41 which supplies the energy to a spark plug 43. Although only one spark plug 43 is shown in FIG. 1, there will be one such spark plug for each cylinder of the engine with which the ignition system is being utilized. In accordance with conventional practice, the distributor 41 selects the particular plug or plugs to which electrical energy is to be supplied for the purpose of developing a spark for ignition of the fuel-air mixture.

The SCR 33 conducts so long as the voltage at the anode with respect to the voltage at the cathode is positive. The SCR 33 is turned off, i.e., rendered nonconductive, in that the discharge of the ignition capacitor 17 causes the potential at the anode to momentarily become negative. This overswing causes the SCR 33 to switch off or into a nonconducting state.

One feature of this invention is the use of the negative voltage spike 31 as a triggering signal for the SCR 33. To accomplish this, the junction J2 is coupled to the cathode of the SCR 33 through a diode 45. The diode 35 is reverse biased by the negative triggering signal 31. The diode 45 is reverse biased by the positive triggering signal 29 and is forward biased by the negative triggering signal 31. Accordingly, the potential at the cathode of the SCR 33 is negative with respect to the potential at the gate, or conversely, the gate is positive with respect to the cathode. This provides a gate signal 46 (FIG. 4) which is similar to the gate signal 36. The gate signal 46 as shown in FIG. 4 renders the SCR 33 conductive a second time to thereby achieve a second discharge of the capacitor 17. Of course, the charging circuit must be capable of recharging the ignition capacitor 17 during the interval between the triggering signals 29 and 31. When the SCR 33 switches to a conductive state, the spark plug 43 is supplied with a second electrical energy pulse of equal intensity sufficient for it to generate a second ignition spark. Thus, dual ignition sparks are provided for each combustible charge with the first one occurring when the points 21 open and the second spark occurring when the points 21 close.

The diode 37 provides a small impedance between the cathode of the SCR 33 and ground so that the voltage at a junction J3 is slightly positive during the time that the capacitor 17 is being discharged as a result of the triggering signal 29. However, this voltage forward biases the diodes 45 and 35 and is applied to the gate of the SCR 33. Accordingly, the diode 37 has substantially no effect on the SCR 33 during discharge of the ignition capacitor as a result of the triggering signal 29. The diode 37 prevents the negative triggering signal 31 from being shorted out when it is applied to the cathode of the SCR 33.

Although FIG. 3 shows the triggering signals 29 to have lesser amplitude than the triggering signals 31, the amplitude of the signals 29 could be equal to or greater than the amplitude of the signals 31. The relative amplitudes of the signals 29 and 31 is a function of the relative resistances of the resistors 47 and 49. In the embodiment illustrated, the resistance of the resistor 49 is higher than the resistance of the resistor 47. A resistor 51 is coupled to ground and to the lead between the junction J3 and the diode 45. The resistor 51 provides a ground reference for the negative triggering pulse 31. The resistor 47 provides a ground reference for the positive triggering signal 29.

Without the timing device 25, the system 11 as described hereinabove will provide two sparks per combustible charge with the first of these sparks occurring when the points 21 open and the second of these sparks occurring when the points 21 close. By using the timing device 25, the second of these sparks can be made to occur at some time other than closure of the points. The timing device 25 is responsive to opening of the points 21 to provide a simulated point closure at a fixed time interval following opening of the points.

The timing device 25 includes an SCR 25 having its anode coupled to the junction J1 and its cathode coupled to ground. The SCR 53 can be rendered conductive by an RC circuit which includes a manually adjustable variable resistor 55 and a capacitor 57. A resistor 59 is coupled to the gate of the SCR 53 and to the resistor 55 and the capacitor 57. By varying the resistance of the resistor 55, the time constant of the RC circuit can be varied.

When the points 21 open and the voltage at the junction J1 rises, the capacitor 57 is charged through the resistor 55 with the time required for such charging to occur being a function of the resistance of the resistor 55. When the capacitor 57 is charged, a positive voltage signal is applied to the gate of the SCR 53 through the resistor 59 to render the SCR 53 conductive. When the SCR conducts, the junction J1 is coupled to ground to thereby simulate closure of the points.

Similarly, when the points 21 open, the voltage at the gate increases at a rate which is a function of the resistance of the variable resistor 55 and the capacitance of the capacitor 57 as shown in FIG. 7. The SCR 53 is switched to a conductive state when the voltage at the gate reaches a magnitude V which may be in the order of one volt. The curves a, b, c and d represent the rate of increase in gate voltage for the SCR 53 for increas ing values of the resistance 55. Thus, the time required to increase the gate voltage to the value V can be varied by adjusting the variable resistor 55. Specifically, each of the curves a, b, c and d reaches a gate voltage V at times t, throught respectively.

FIG. 6 shows in solid lines the variation in voltage at J1 with respect to time assuming that the SCR 53 is rendered conductive prior to closure of the points 21. Thus, the voltage at J1 rises to a positive value of V and remains there so long as the points are open and the SCR 53 is in a nonconductive state. However, once the SCR 53 is rendered conductive, the voltage at the junction J 1 drops to a positive value V the magnitude of which equals the voltage drop across the SCR 53 from anode to ground. The voltage level V is maintained until the points close at which time the voltage at the junction J1 drops to O or ground potential. This pattern is then repeated each time the points open. The SCR 53 conducts so long as the voltage at the junction J1 is maintained at themagnitude of V Thus, the SCR 53 is rendered nonconductive when the voltage at the junction J1 drops to 0 as a result of closing the points 21.

With reference to FIGS. 6 and 7, the sharp rise in potential at the junction J1 from O to V, at time I, caused by opening of the points constitutes a first timing signal. The sharp drop in potential at the junction J 1 resulting from the SCR 53 switching to a conductive condition at the time t constitutes the second timing signal. The interval between these timing signals does not vary with engine speed, but it can be changed, as shown by dashed lines in FIGS. 6 and 7, by varying the resistance of the resistor 55. The closing of the points 21 does not provide a timing signal unless the points 21 close before the SCR 53 is switched into conduction.

FIG. 8 shows how the time at which the negative triggering pulse 31 occurs can be controlled by the second timing signal or the time at which the SCR 53 is switched to a conducting state. Specifically, the triggering signals 31 shown in dashed lines correspond to dif-' ferent settings of the variable resistor 55.

FIG. 5 shows how the second gate signal 46 occurs when the SCR 53 is rendered conductive or when the points 26 close, whichever occurs first. The gate signals 46 shown in dashed lines correspond to different settings of the variable resistor 55. The operation of the system as shown in FIGS. 8 is identical to that described with reference to FIGS. l4 except that the second timing signal, and hence the second ignition spark for each combustible charge, can be caused to occur with the points 21 open.

As is well known, the timing of an ignition system can be adjusted so that the points 21 close at different angular positions of the crank with ignition typically occurring at some time before top dead center of the compression stroke. Furthermore, distributors often have various means to automatically adjust the timing the accordance with various parameters such as engine speed.

FIG. 9 shows by way of example and not be way of limitation one way in which the opening and closing of the points 21 can vary automatically in response to engine speed. As shown in FIG. 9, the conventional centrifugal advance system of the distributor 41 causes the points to open at 10, and 30", respectively, before top dead center for engine speeds of 1,000, 2,000 and 3,000 rpms, respectively. The degrees referenced in connection with FIG. 9 are crankshaft degrees rather than camshaft degrees. In the example shown in FIG. 9, after 3,000 rpms the spark is not further advanced. The points close at 20 and 10 after top dead center and at top dead center for speeds of 1,000 rmp, 2,000 rpm and 3,000 rpm, respectively.

To illustrate how the timing device can be employed, assume that it is desired to have the second spark occur at top dead center. The variable resistance 55 can then be adjusted so that at 1,000 rpm the time interval between opening ofthe points and triggering of the SCR 53 is just sufficient for the crankshaft to turn through 10. By way of example, this time interval may be 0.0017 second. If the engine is accelerated to 2,000 rpm, then the points open at 20 before top dead center and close 10 after top dead center (FIG. 9). However, the second or trailing spark will still occur at top dead center because the crankshaft will turn through 20 at 2,000 rpm in the same period of time that it turned through 10 at 1,000 rpm, i.e., in 0.0017 second.

Similarly, at 3,000 rpm, the points open at before top dead center and close at top dead center. Thus, at this speed conduction of the SCR 53 and point closure would occur substantially at the same time. For speeds above 3,000 rpm in this example, the spark is not further advanced so that for higher speeds the second spark will also occur at top dead center.

Although exemplary embodiments of the invention have been shown and described, many changes, modifications and substitutions may be made by one having ordinary skill in the art without necessarily departing from the spirit and scope of this invention.

I claim:

1. An engine ignition system electrically connectible to a source of electrical energy and to first timing means which is repetitively switchable between first and second states in accordance with engine speed, said ignition system comprising:

second timing means having first and second conditions and responsive to the first timing means being in said second state for assuming said second condition a predetermined time following the switch- 0 ing of said first timing means to said second state;

triggering means for providing a first triggering signal in response to each switching of said first timing means to said second state and a second triggering signal in response to the first to occur of said first state and said second condition following each of said first triggering signals; and

means responsive to said first triggering signal for providing a first pulse of electrical energy for ignition and responsive to said second triggering signal for providing a second pulse of electrical energy for ignition.

2. An engine ignition system as defined in claim 1 wherein said triggering means includes a triggering capacitor electrically connectible to the source of electrical energy to thereby enable said capacitor to be charged, said second timing means including means for discharging said capacitor to thereby provide one of said triggering signals.

3. An engine ignition system as defined in claim 2 wherein said discharging means includes an SCR and a resistive-capacitive circuit for triggering said SCR, the resistive-capacitive circuit having a time constant for providing a time delay substantially equal to said predetermined time.

4. An engine ignition system as defined in claim 3 including means for varying the time constant of said circuit to thereby vary said predetermined time.

5. An engine ignition system as defined in claim 1 including means for varying said predetermined time.

6. An engine ignition system as defined in claim 1 wherein each of said first triggering signals is of a different polarity than each of said second triggering signals.

7. An engine ignition system wherein a first conduc tive path is electrically connectible to a source of electrical energy and timing means repeatedly opens and closes the first conductive path in accordance with engine speed, said engine ignition system comprising:

a second conductive path electrically connectible to a reference potential and to the first conductive path at a junction;

electronic switch means in said second conductive path, for opening and closing said second conductive path said junction being at a first potential when said first and second conductive paths are opened by said timing means and said electronic switch means, respectively, and at a second potential when either of said first and second conductive paths is closed by said timing means and said electronic switch means, respectively, said first and second potentials being different;

first means responsive to the potential of said junction changing from said first potential to said second potential for providing a first pulse of energy for use in igniting the fuel for the engine and responsive to the potential of said junction changing from said second potential to said first potential for providing a second pulse of energy for use in igniting the fuel for the engine; and

means for controlling the opening and closing of said electronic switch including means for rendering said electronic switch conductive a predetermined interval after opening of the first conductive path whereby the first to close of conductive paths controls the timing of the first pulse.

8. An engine ignition system as defined in claim 7 wherein said last mentioned means includes means responsive to the opening of the first conductive path for closing said electronic switch a predetermined time ible to a source of electrical energy and to timing means for repetitively providing first and second timing signals, said ignition system comprising:

after said timing means opens said first conductive path.

9. An engine ignition system as defined in claim 8 llO. An engine ignition system electrically connecttriggering means responsive to said timing signals for providing a positive electrical triggering signal in response to each of said first timing signals and a negative electrical triggering signal in response to each of said second timing signals;

capacitive means for storing electrical energy, said capacitive means being dischargeable to provide a pulse of electrical energy for use in ignition;

first means for discharging said capacitive means in response to each of said triggering signals;

said first means including an SCR which has conductive and nonconductive states and second means for rendering said SCR conductive in response to 'each of said positive and negative triggering signals; and

said second means including means for applying said negative triggering signal to the cathode of the SCR and means for causing the gate of the SCR to be positive with respect to the cathode when said negative triggering signal is applied to the cathode.

11. An engine ignition system electrically connectible to a source of electrical energy and to timing means for repetitively providing first and second timing signals, said ignition system comprising:

first means for discharging said capacitive means in response to each of said triggering signals;

said first means including an SCR which has conductive and nonconductive states and second means for rendering said SCR conductive in response to each of said positive and negative triggering signals; and

said second means including a first conductive path between the triggering means and the gate of the SCR, a second conductive path between the triggering means and the cathode of the SCR, first semiconductor means in said first conductive path for allowing the positive triggering signal to be applied to the gate of the SCR to render the latter conductive and for blocking the negative triggering signal, and second semiconductor means in said second path for allowing the negative triggering signal to be applied to the cathode of the SCR to render the latter conductive and for blocking the positive triggering signal.

12. An engine ignition system as defined in claim 11 including a third conductive path coupled to said second conductive path and to a reference potential and a third semi-conductor means in said third conductive path for blocking the negative triggering signal.

13. An engine ignition system as defined in claim 6 wherein said last mentioned means includes an SCR, means for applying said first triggering signal to the gate of the SCR to trigger the SCR, means for applying the second triggering signal to the cathode of the SCR to trigger the SCR, and means for providing one of said pulses of electrical energy in response to each triggering of the SCR.

14. An engine ignition system as defined in claim 7 wherein said first means includes a capacitor coupled to said junction, said capacitor initially conducting upon the potential at said juncture being at said first potential to provide a positive triggering signal, said capacitor discharging upon saidjuncture being brought to said second potential to provide a negative triggering signal, and means for providing said first and second pulses in response to said negative and positive triggering signals, respectively. 

1. An engine ignition system electrically connectible to a source of electrical energy and to first timing means which is repetitively switchable between first and second states in accordance with engine speed, said ignition system comprising: second timing means having first and second conditions and responsive to the first timing means being in said second state for assuming said second condition a predetermined time following the switching of said first timing means to said second state; triggering means for providing a first triggering signal in response to each switching of said first timing means to said second state and a second triggering signal in response to the first to occur of said first state and said second condition following each of said first triggering signals; and means responsive to said first triggering signal for providing a first pulse of electrical energy for ignition and responsive to said second triggering signal for providing a second pulse of electrical energy for ignition.
 2. An engine ignition system as defined in claim 1 wherein said triggering means includes a triggering capacitor electrically connectible to the source of electrical energy to thereby enable said capacitor to be charged, said second timing means including means for discharging said capacitor to thereby provide one of said triggering signals.
 3. An engine ignition system as defined in claim 2 wherein said discharging means includes an SCR and a resistive-capacitive circuit for triggering said SCR, the resistive-capacitive circuit having a time constant for providing a time delay substantially equal to said predetermined time.
 4. An engine ignition system as defined in claim 3 including means for varying the time constant of said circuit to thereby vary said predetermined time.
 5. An engine ignition system as defined in claim 1 including means for varying said predetermined time.
 6. An engine ignition system as defined in claim 1 wherein each of said first triggering signals is of a different polarity than each of said second triggering signals.
 7. An engine ignition system wherein a first conductive path is electrically connectible to a source of electrical energy and timing means repeatedly opens and closes the first conductive path in accordance with engine speed, said engine ignition system comprising: a second conductive path electrically connectible to a reference potential and to the first conductivE path at a junction; electronic switch means in said second conductive path, for opening and closing said second conductive path said junction being at a first potential when said first and second conductive paths are opened by said timing means and said electronic switch means, respectively, and at a second potential when either of said first and second conductive paths is closed by said timing means and said electronic switch means, respectively, said first and second potentials being different; first means responsive to the potential of said junction changing from said first potential to said second potential for providing a first pulse of energy for use in igniting the fuel for the engine and responsive to the potential of said junction changing from said second potential to said first potential for providing a second pulse of energy for use in igniting the fuel for the engine; and means for controlling the opening and closing of said electronic switch including means for rendering said electronic switch conductive a predetermined interval after opening of the first conductive path whereby the first to close of conductive paths controls the timing of the first pulse.
 8. An engine ignition system as defined in claim 7 wherein said last mentioned means includes means responsive to the opening of the first conductive path for closing said electronic switch a predetermined time after said timing means opens said first conductive path.
 9. An engine ignition system as defined in claim 8 wherein said means for closing said electronic switch includes a resistive-capacitive circuit coupled to said second path and receiving electrical energy therefrom, said resistive-capacitive circuit providing said predetermined time.
 10. An engine ignition system electrically connectible to a source of electrical energy and to timing means for repetitively providing first and second timing signals, said ignition system comprising: triggering means responsive to said timing signals for providing a positive electrical triggering signal in response to each of said first timing signals and a negative electrical triggering signal in response to each of said second timing signals; capacitive means for storing electrical energy, said capacitive means being dischargeable to provide a pulse of electrical energy for use in ignition; first means for discharging said capacitive means in response to each of said triggering signals; said first means including an SCR which has conductive and nonconductive states and second means for rendering said SCR conductive in response to each of said positive and negative triggering signals; and said second means including means for applying said negative triggering signal to the cathode of the SCR and means for causing the gate of the SCR to be positive with respect to the cathode when said negative triggering signal is applied to the cathode.
 11. An engine ignition system electrically connectible to a source of electrical energy and to timing means for repetitively providing first and second timing signals, said ignition system comprising: triggering means responsive to said timing signals for providing a positive electrical triggering signal in response to each of said first timing signals and a negative electrical triggering signal in response to each of said second timing signals; capacitive means for storing electrical energy, said capacitive means being dischargeable to provide a pulse of electrical energy for use in ignition; first means for discharging said capacitive means in response to each of said triggering signals; said first means including an SCR which has conductive and nonconductive states and second means for rendering said SCR conductive in response to each of said positive and negative triggering signals; and said second means including a first conductive path between the triggering means and the gate of the SCR, a second conductive path between the triggeriNg means and the cathode of the SCR, first semiconductor means in said first conductive path for allowing the positive triggering signal to be applied to the gate of the SCR to render the latter conductive and for blocking the negative triggering signal, and second semiconductor means in said second path for allowing the negative triggering signal to be applied to the cathode of the SCR to render the latter conductive and for blocking the positive triggering signal.
 12. An engine ignition system as defined in claim 11 including a third conductive path coupled to said second conductive path and to a reference potential and a third semi-conductor means in said third conductive path for blocking the negative triggering signal.
 13. An engine ignition system as defined in claim 6 wherein said last mentioned means includes an SCR, means for applying said first triggering signal to the gate of the SCR to trigger the SCR, means for applying the second triggering signal to the cathode of the SCR to trigger the SCR, and means for providing one of said pulses of electrical energy in response to each triggering of the SCR.
 14. An engine ignition system as defined in claim 7 wherein said first means includes a capacitor coupled to said junction, said capacitor initially conducting upon the potential at said juncture being at said first potential to provide a positive triggering signal, said capacitor discharging upon said juncture being brought to said second potential to provide a negative triggering signal, and means for providing said first and second pulses in response to said negative and positive triggering signals, respectively. 